docs: def overlapping(self, start=None, end=None):
          """
          :return: occurrences overlapping the given start and end datetimes,
          inclusive.
          Special logic is applied for all-day occurrences, for which the start
          and end times are zeroed to find all occurrences that occur on a DATE
          as opposed to within DATETIMEs.
          """
          qs = self
  
          if start:
              dt_start=coerce_dt_awareness(start)
              qs = qs.filter(
                  # Exclusive for datetime, inclusive for date.
                  Q(is_all_day=False, end__gt=dt_start) |
                  Q(is_all_day=True, end__gte=zero_datetime(dt_start))
              )
          if end:
              dt_end=coerce_dt_awareness(end, t=time.max)
              qs = qs.filter(
                  Q(is_all_day=False, start__lt=dt_end) |
                  Q(is_all_day=True, start__lt=zero_datetime(dt_end))
              )
  
          return qs